Catalytic hydrocracking of naphthas with the use of a catalyst composite comprising copper on a siliceous support



United States Patent 3,303,124 CATALYTIC HYDROCRACKING OF NAPHTHAS WITHTHE USE OF A CATALYST COMPOSITE COMPRISING COPPER ON A SILICEOUS SUP-PORT Clarence W. Bittner, Orinda, Calif., assignor to Shell Oil Company,New York, N.Y., a corporation of Delaware N0 Drawing. Filed Dec. 24,1964, Ser. No. 421,094 6 Claims. (Cl. 208-111) This application is acontinuation-in-part of applicants copending US. application, Serial No.325,793, filed November 22, 1963 (now abandoned).

This invention relates to a process for the catalytic conversion ofhydrocarbons, particularly paraffinic naphtha fractions to low boilinghigh octane gasoline components.

In the refining of petroleum, various hydrocarbon fractions boiling inthe gasoline boiling range are recovered and are appropriately blendedto provide a finished gasoline. Gasoline components include, forexample, straightrun gasoline fractions obtained from the distilling ofcrude oil, cracked fractions obtained from the conversion of hydrocarbonfractions boiling above the gasoline boiling range, and polymer andalkylate fractions derived from reacting low boiling normally gaseoushydrocarbons.

The trend has been to higher octane gasolines to satisfy the demands ofmodern high compression ratio automotive engines. Aromatic hydrocarbonshave quite high octane ratings, therefore, preference has been given toaromatic rich hydrocarbon fractions as a component for finished highoctane gasoline, Aromatic rich hydrocarbon fractions are obtained fromcracking high boiling fractions and catalytically reformingnaphthasnaphthenic straightrun naphthas primarily but cracked naphthasare often included as well. The aromatic content of such aromaticrichhydrocarbon fractions can be concentrated more by such means asextractive distillation or extraction with selective solvents such asglycols, sulfolane and the like.

Since aromatic hydrocarbons are relatively high boiling gasolinecomponents, low boiling components such as C and C hydrocarbons are usedto provide a finished gasoline of balanced volatility. The C and Cisoparaflins are desired as the octane rating is much better than forthe corresponding normal parafiins and octane senssitivity (researchoctane rating minus motor octane rating) is much better for thecorresponding olefins. However, light straight-run C /C fractions arecomprised largely of normal paraflins. To upgrade these lightstraight-run fractions, resort must be had to isomerization with suchcatalysts as a Friedel-Crafts catalyst or a supported platinum catalyst.Yet, isomerization processes have a serious disadvantage in thatconversion is limited by thermodynamic equilibrium. Thus, isoparaflin tonormal paraffin ratios in the product are relatively low, e.g. on theorder of 23:1. Recovery and recycle of unconverted normal paraffins addsgreatly to the cost of an isomerization rocess.

There remains, then, parafiinic naphthas such as the straight-runnaphthas which are less desirable for reforming feed or the rafiinatesobtained from the extraction of catalytic reformates. These paraffinicnaphthas boiling in the range from about 200 F. to 450 F. have lowoctane rating and are much less desirable as gasoline blendingcomponents. A process for upgrading such paraffinic naphthas obviouslyis desirable.

In accordance with the process of this invention, paraflinic naphthasare selectively converted to low boiling C -C hydrocarbons having a highiso to normal paraffin ratio by means of an active catalyst comprisingcopper and an acid-acting refractory oxide cracking catalyst at anelevated temperature and pressure and in the presence of hydrogen.

Naphthas which are converted in the process of the invention are theparafiinic naphthas boiling in the range from about 200-450 F. Byparaffinic naphthas it is meant those naphthas which are predominantly,i.e. about 60% by volume and preferably about by volume or moreparatfins. Moreover, it is preferred that such naphthas contain lessthan about 10% by volume of aromatic hydrocarbons. Higher boilingparaffins can be included,

if desired.

The catalyst used in the present process is a multifunctional catalystcomposition which comprises copper incorporated with an acid-actingrefractory oxide cracking catalyst. Acid-acting refractory oxidecracking catalyst are generally the amorphous siliceous materials suchas silica in combination with one or more oxides such as alumina,magnesia, zirconia, titania and the like. Silicaalnmina is a well knowand widely used cracking catalyst and is highly suitable for use in thepresent invention. In general, silica-content of the cracking componentis in the range from about 60% to by weight.

The copper catalyst is prepared by incorporating copper in a hydrogel ofthe siliceous refractory oxide cracking catalyst such as byion-exchanging copper cations into the hydrogel. Surprisingly, activityof a copper catalyst prepared by incorporating the copper into asiliceous hydrogel is markedly superior to a catalyst wherein thehydrogel is dried and calcined and copper is deposited thereonv by theconventional impregnation technique. The reason for the markedly higheractivity is not known. It is possible that the presence of the copperions in the hydrogel stabilize or help maintain active cracking siteswhich otherwise are lost during calcination. With silicaalumina, forexample, it is the general practice to form a hydrogel from sodiumsalts, especially sodium silicate. Sodium ions are then washed from thehydrogel by means of ammonium salts or by acidulated water (e.g. watertreated with solid ion-exchange resins to remove metallic cations) whichleaves volatile cations to maintain the structure. Upon calcination ofthe hydrogel, the volatile cations and water are removed whichpresumably allows collapse or reorientation to a less active'structure.Incorporation 'of copper cations into the hydrogel prior to calcinationpresumably tends to stabilize and maintain a highly active orientation.

As the catalyst is multifunctional, it might also be expected thatcopper bound within the silica-alumina structure would be less availablefor contact with hydrocarbon and would be, therefore, of reducedactivity compared with an impregnated catalyst where the metal isdeposited on a preformed silica-alumina support. On the contrary, theimpregnated catalysts are much less active. A possible explanation isthat the impregnating solution on the catalyst becomes more concentratedas solvent, such as water, gradually is evaporated. Moreover, theremaining solution is drawn within the catalyst pores by capillaryaction. Thus, when all the solvent has been evaporated from theimpregnating solution, the copper compound is deposted in the form ofcrystallites whose diameters are comparable to the diameters of thecatalyst pores.

corporating the copper in a hydrogel provides a wide degree ofdispersion of the copper most of which at least apparently is retainedas the catalyst is dried and calcined.

Any suitable means for preparing a siliceous hydrogel can be used forthe present catalyst. For example, the preparation of silica-aluminacracking catalyst is Well known and hence need not be discussed here.The copper is incorporated into the hydrogel prior to calcination of thehydrogel. The amount of copper in the fi'nal catalyst is in the rangefrom about 0.1-25% by weight, preferably about 1-15% by weight.

It is generally advantageous to incorporated promoters such as fluorineinto the catalyst. Incorporation of fluorine into, for example,silica-alumina hydrogel is considered to enhance the eifectivness of thecopper and of the acidic or cracking function. The presence of fluorinein the hydrogel apparently results in a more complete interaction of themetal ion with silica-alumina gel. The

amount of fluorine can vary from about 0.1% to about by weight andpreferably is about 1% to 3% by weight, based on the total weight of thecatalyst. The fluorine can be incorporated into the catalyst in anysuitable manner such as co precipitation by adding fluoride compounds tothe solution from which silica and alumina are precipitated to formsilica-alumina hydrogel. Another method is to contact the hydrogel withfluoride compounds.

Incorporation of copper into a siliceous gel such as silica-aluminahydrogel provides a catalyst which is highly active for the selectiveconversion of the paraflinic naphthas and which appears to be resistantto poisoning by nitrogen compounds. Nitrogen compounds are generallyconsidered to be quite poisonous to acidic catalysts. With mostparafli-nic naphtha feeds, no pretreatment to remove nitrogen compoundsis necessary in the present process and is in contrast to usualhydroprocesses which employ acidic cracking catalysts. Rafiinatesrecovered in the extraction of catalytic reformates, or course, normallywill be quite low in nitrogen and sulfur compounds.

In the process of the invention the paraflinic hydrocarbon feed isintroduced into a reaction zone with a large excess of hydrogen. Theamount of hydrogen employed is expressed in terms of hydrogen to oilmole ratio and is in the range from about 5:1 to about 25:1 or more. Theconversion reaction is accompanied by a rather large consumption ofhydrogen usually of the order of 500 to about 1500 standard cubic feetof hydrogen per barrel of feed converted. Conversion herein refers tothe products obtained which boil below 200 F. Excess hydrogen isgenerally recovered at least in part from the reaction zone effluent andrecycled to the reactor'together with additional makeup hydrogen. Purehydrogen is not necessary as any suitable hydrogen-com taining gas whichis predominantly hydrogen can be used, Particularly suitable is thehydrogen-rich gas containing on the order of 7090% hydrogen which isobtained from a catalytic reforming process.

Pressure employed in the selective conversion reaction is in excess ofabout 500 p.s.i.-g. and can range up to as high as about 3000 p.s.i.g.or so, a preferred range being from about 1000 to 2000 p.s.i.-g. Averagetemperature in the reaction zone is in the range from about 450 to 850F. The conversion reaction is exothermic; therefore, it is generallydesired to provide some means of cooling the reaction zone, such as bythe injection of relatively cold hydrogen. Liquid hourly space velocitycan be in the range from about 0.1 to 25 and preferably from about 1 to10.

EXAMPLE I Silica-alumina which had been prepared in a conventionalmanner comprising the precipitation of silica from sodium silicatesolution, precipitation of alumina onto the silica, removal of sodiumions from the hydrogel, and calcination of the hydrogel, was preformedinto pellets and impregnated with a copper nitrate and HF solution. The

. 4' silica-alumina contained about 25% by weight alumina and thefinished catalyst nominally contained 5.0% by weight copper and 2.5% byweight fluorine.

Another catalyst was prepared wherein copper was incorporated intosilica-alumina hydrogel before calcination. To a solution of sodiumsilicate was added a solution of sodium alu-minate and sodium fluoridefollowed by the addition of sulfuric acid to adjust the pH to about 7.The proportions were such as to provide 2.5 w. F. and about 30% w. A1 0in the finished silica-alumina. The hydrogel which formed was recoveredby filtration and given repeated washings with ammonium nitrate solutionand water to remove substantially all sodium cations from the hydrogel.The washed hydrogel was slurried in an ammoniacal solution of coppernitrate to ionexchange copper cations into the hydrogel. Theion-exchanged .hydrogel was washedwith water to remove excess coppernitrate, dried, and calcined at about 1100 F. The finished catalystcontained 4.7% w. copper.

Each catalyst was employed to convert normal decane at 617 F. (325 C.),1500 p.s.i.g., 10/1 H /oil mole ratio, and at various liquid hourlyspace velocities (volu-mes of oil per volume of catalyst per hour). Theresults are given in Table 1 below.

Table I Impregnated Copper Ion-exchanged Copper LHSV 4. 0 8. 4 3. 9 7. 7Conversion, percent w 48. 2 36.6 90. 4 70. 9 Product analysis,

p rcent w 0. 1 0. 1 0. 2 0. 1 3. 2 2. 1 8. 4 7. 4 12. 8 9. 2 27. 6 23.112. 5 9. 9 27. 3 20. 5 12.2 8. 5 23. 1 15. 3 C7-C9 4. 9 4.1 3.1 3. 3i-Cw 2. 4 2. 6 0.6 1. 1 n-Cio 51. 8 63. 4 9. 6 29.1 011+ 0.2 0.2 0.1 0.1Iso/normal paraffin ratio:

04 4. 0 3. 8 3. 6 3. 5 C5 7. 4 8. 7 3. 8 5. 0 On 8. 5 8. 9 4. 3 5. 4

Based on extrapolated space velocities to provide equivalent conversionthe catalyst wherein copper was incorporated into the hydrogel is 4-5times more active than the catalyst wherein copper was impregnated ontoa calcined hydrogel.

It is also to be noted that in general, yield of light gases decreasesand the isoparaflin to normal paraflin ratio increases as conversion isdecreased.

I claim as my invention:

1. A process for converting a paraflinic naphtha having at least 60% byvolume paraflins and boiling in the range from about 200 to 450 F. intolight gasoline boiling below about 200 P. which comprises contactingsaid naphtha at a temperature in the range from about 450 to 850 F., apressure in the range from about 500 to 3000 pounds per square inch anda hydrogen to oil mole ratio in the range from about 5:1 to 25: 1; witha catalyst comprising copper intimately associated with an acid-actingsiliceous refractory oxidecraoking catalyst, said catalyst having beenformed by incorporating the copper into a hydrogel of the refractoryoxide.

2. The process according to claim 1 wherein the naphtha comprises araflinate from a catalytic reformate.

3. The process according to claim 1 wherein the refractory oxide issilica-alumina.

4. A process for converting a paraflinic naphtha having at least 60% byvolume paraflins and boiling in the range from about 200 to 450 F. intolight gasoline boilingbelow about 200 F. which comprises contacting saidnaphtha at a temperature in the range from about 450 to 850 F., apressure in the range from about 500 to 3000 pounds per square inch and'a hydrogen to oil mole ratio in the range from about 5:1 to 25: 1, witha catalyst comprising copper intimately associated with an acidactingsiliceous refractory oxide cracking catalyst, said catalyst having beenformed by contacting a hydrogel of the refractory oxide with a solutionof a copper compound wherein the copper is present as a cation toexchange copper cations into the hydrogel.

5. The process according to claim 4 wherein the refractory oxide issilica-alumina.

6. The process according to claim 5 wherein the naphtha comprises araflinate from a catalytic reformate.

References Cited by the Examiner UNITED STATES PATENTS Voorhies 208112Hennig 20896 Wilson 2081 11 Wilson 2081 11 DELBERT E. GANTZ, PrimaryExaminer.

10 ABRAHAM RIMENS, Examiner.

1. A PROCESS FOR CONVERTING A PARAFFINIC NAPHTHA HAVING AT LEAST 60% BYVOLUME PARAFFINS AND BOILING IN THE RANGE FROM ABOUT 200* TO 450*F. INTOLIGHT GASOLINE BOILING BELOW ABOUT 200*F. WHICH COMPRISES CONTACTINGSAID NAPHTHA AT A TEMPERATURE IN THE RANGE FROM ABOUT 450* TO 850*F., APRESSURE IN THE RANGE FROM ABOUT 500 TO 3000 POUNDS PER SQUARE INCH ANDA HYDROGEN TO OIL MOLE RATIO IN THE RANGE FROM ABOUT 5:1 TO 25:1; WITH ACATALYST COMPRISING COPPER INTIMATELY ASSOCIATED WITH AN ACID-ACTINGSILICEOUS REFRACTORY OXIDE CRACKING CATALYST, SAID CATALYST HAVING BEENFORMED BY INCORPORATING THE COPPER INTO A HYDROGEL OF THE REFRACTORYOXIDE.